Title : A case of neurosyphilis presenting as dyschromatopsia in an immunocompetent Filipino adult
Abstract:
Background: Syphilis, caused by Treponema pallidum, is a multisystemic sexually transmitted infection recognized as a “great imitator.” Ocular syphilis, a manifestation of neurosyphilis, can occur at any stage and affect nearly all ocular structures presenting with symptoms ranging from pain and blurred vision to complete blindness. In the Philippines, syphilis accounted for 1,157 deaths in 2020, ranking 39th globally, yet epidemiologic data on neurosyphilis in Asia and in the Philippines remain scarce up until today. Although commonly associated with HIV infection, ocular syphilis may also occur in immunocompetent individuals. We present a case of neurosyphilis manifesting as dyschromatopsia, highlighting the challenge in committing to treatment in the setting of inconclusive diagnostics in order to avoid permanent visual loss.
Case: This is a case of a 37-year-old, male, Filipino with history of sex with men who had three months of constitutional symptoms, including fatigue, fever, sore throat, and a generalized maculopapular rash. Two weeks before admission, he developed progressive dyschromatopsia, initially affecting red-green perception, leading to bilateral blurring of vision. Physical exam showed generalized lymphadenopathy, patchy alopecia and hyperpigmented macules. Visual acuity was 20/20 with Ishihara scores of 12/15 bilaterally. Baseline fundoscopic findings revealed right optic papillitis with bilateral retinal vasculitis and a left hemianopic defect on perimetry. No other pertinent neurologic physical finding was observed. Serology showed a reactive TPHA with non reactive VDRL/RPR, and negative results for HIV RNA, Hepatitis B surface antigen, and Hepatitis C. Brain with orbital MRI and visual evoked potentials were all normal. A lumbar tap was done and CSF analysis revealed lymphocytic pleocytosis, CSF total protein of 50mg/dl. However, CSF VDRL was non reactive. No pathogen was detected on Multiplex PCR meningitis and encephalitis assay. Based on strong clinical suspicion for ocular syphilis, intravenous Penicillin G of 4 million units IV every 4 hours for 14 days was given with gradual improvement on the Ishihara scores at 15/15 and resolving optic neuropathy bilaterally at completion of 14 days of penicillin G infusion. No corticosteroid was given.
Discussion: Patients with ocular symptoms and reactive syphilis serology should undergo a comprehensive ophthalmologic exam. The most frequent findings are panuveitis—especially in HIV-positive patients—and posterior uveitis in HIV-negative individuals; chorioretinitis is also common. CSF analysis is indicated when cranial nerve deficits are present. Neurosyphilis is supported by neurologic symptoms plus CSF abnormalities (pleocytosis, elevated protein, or reactive CSF-VDRL) with positive treponemal serology. Because no single test is definitive, all results must be interpreted in the context of the patient’s overall clinical picture and pretest probability.
Conclusion: This case underscores the challenges in diagnosing neurosyphilis. Prompt recognition and empiric treatment are critical in preventing irreversible visual loss.
